Abstract: This paper establishes a leaking consequent model to evaluate the hazards and loss from fire and burst due to leaking of city gas pipelines. Models to calculate gas leaking volume and for pipeline failure are listed, and three models for gas leaking consequence are presented. Gauss Diffusion Model are used to simulate distributive scope of flammable gas concentration, a model calculating heat radiation radius of fire is presented and a new TNT coefficient method by conventional TNT method to assess the effectiveness of shock wave of the burst is established. The model established is of benefit to line out the safe distance in rush repair and to determine dangerous zone, and can minimize the fire or burst in gas leaking event.